Dust Or Spray For All Over Shimmer

Hi all,I will be making a cake covered in gray fondant with an all over sparkle/shimmer effect. I've considered either brushing with dry pearl dust or the edible pearl spay. Any suggestions about which would be better? How much of either would I need to completely cover a 6", 9", and 12" round?Thanks in advance!

Thank you for your reply BlakesCakes! Looks like that would be the less expensive option. Do you find the spray cans difficult to control at all? I don't want it to be to heavy and I'm a little concerned about getting even coverage since I don't have any experience with that. Thanks again!